feat(kyberforge): refresh the apm install at SessionStart, not at push

Why
---
ADR-0018 left deployed skills tracking the remote default branch with nothing
watching for drift. The mechanism that was supposed to cover this,
scripts/git-hooks/post-push, could never have worked: git has no client-side
post-push hook. install.sh copied it into .git/hooks/ so it looked installed,
and it had never once fired. Issue #78 reported it as skipping the gitea
plugin; it was skipping everything.

Refreshing on push was also the wrong shape. Your install goes stale when
someone else merges, so a push of your own is neither necessary nor sufficient
for staleness to have occurred.

Implementation notes
--------------------
kyberforge ships a SessionStart hook (startup matcher only) that runs
`apm outdated`, and when anything is behind runs `apm update --yes` and returns
reloadSkills:true so the running session picks up redeployed content. It exits
silently with no apm.lock.yaml present, which keeps it inert for hosts that
installed this plugin natively rather than through apm.

Two findings drove the wiring, both verified rather than assumed:

- apm resolves ${CLAUDE_PLUGIN_ROOT} against the installed package root, and
  `apm pack` keeps only *.json from .apm/hooks/. A .../hooks/<script> reference
  therefore points into the generated mirror where the script does not exist —
  apm reports "Hook script not found" and deploys a hook aimed at nothing. The
  reference must be .apm/-relative, and a test pins it.
- apm's executable-trust gate is OFF unless apm.yml carries an `executables:`
  block; until now every hook, bin and MCP primitive a dependency shipped would
  have deployed unprompted. Root apm.yml now enables it. The allow key is
  version-pinned by apm's design, so a kyberforge version bump silently blocks
  the hook until the key is bumped too — called out in the block and the ADR.

Also corrects ADR-0018 and AGENTS.md, which named `apm install` as the refresh
command. It is not: `apm install` deploys from apm.lock.yaml's pinned commit
and does not re-resolve refs. `apm update` does.

Impact
------
Session startup costs ~0.7s when current and ~10.4s when six packages are
behind. Auto-refresh rewrites apm.lock.yaml, so an unexplained modification to
it after opening a session is expected; the emitted notice says so.

.claude/settings.json stops being exactly {"hooks": {}} once the hook lands
there — the merged entry is apm's own output, and the rule that nothing
repo-authored goes in that file is unchanged. .claude/hooks/ and the
.claude/apm-hooks.json sidecar are gitignored install output.

The hook cannot install itself: dependencies resolve from the remote, so it
takes effect only after this merges and `apm update` runs once against the new
default branch.

scripts/git-hooks/ is now empty. install.sh's copy block is kept and
test-git-hooks-install.sh synthesizes its own fixture, so the mechanism stays
tested without requiring a dead hook to exist.

ADR: 0019
Refs: #78

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01X7GvKuJfy2WrdBmUttV4DT

AGENTS.md

@@ -37,8 +37,9 @@ Fall back to raw shell only when no skill covers it.
 
 ## Setup and testing
 
-- Run `apm install` to deploy this repo's own skills and agents into `.claude/skills/` and `.claude/agents/`. Both are gitignored install output, not authoring source — `plugins/<name>/.apm/` remains the only place to edit. The six dependencies in root `apm.yml` resolve from the holocron **remote**, unpinned against the default branch, so a `.apm/` edit is not visible to the running session until it is pushed and `apm install` re-runs. Needs the network, and needs `apm_modules/` (which it materializes) left gitignored. `apm install` also configures the `obsidian` MCP server into the repo's `.mcp.json`, carried over from `plugins/bin/.mcp.json`.
-- Do not add repo-owned keys to `.claude/settings.json`. apm treats that file as its own deployed artifact: `apm audit --ci` replays the install into a scratch tree and diffs, so anything apm would not have written there — an `enabledPlugins` block, a real `hooks` entry — is permanent drift that fails the `apm-audit-ci` pre-push hook. The file's committed content is exactly `{"hooks": {}}`. Machine-specific settings go in the gitignored `.claude/settings.local.json`, which apm does not deploy and the replay does not compare; shared enforcement belongs in `.pre-commit-config.yaml`.
+- Run `apm install` to deploy this repo's own skills and agents into `.claude/skills/` and `.claude/agents/`. Both are gitignored install output, not authoring source — `plugins/<name>/.apm/` remains the only place to edit. The six dependencies in root `apm.yml` resolve from the holocron **remote**, unpinned against the default branch, so a `.apm/` edit is not visible to the running session until it is pushed and `apm update` re-runs (`apm install` deploys from `apm.lock.yaml` and does not re-resolve refs). Needs the network, and needs `apm_modules/` (which it materializes) left gitignored. `apm install` also configures the `obsidian` MCP server into the repo's `.mcp.json`, carried over from `plugins/bin/.mcp.json`.
+- Do not add repo-owned keys to `.claude/settings.json`. apm treats that file as its own deployed artifact: `apm audit --ci` replays the install into a scratch tree and diffs, so anything apm would not have written there — an `enabledPlugins` block, a real `hooks` entry — is permanent drift that fails the `apm-audit-ci` pre-push hook. Its committed content is whatever apm last wrote — `{"hooks": {}}` until kyberforge's `SessionStart` hook lands there, after which the merged hook entry is apm's output and belongs in the commit (ADR-0019). What does not change is that nothing repo-authored goes in the file. A hook you want in this repo is authored in `plugins/<name>/.apm/hooks/` and deployed by apm, never hand-written here. Machine-specific settings go in the gitignored `.claude/settings.local.json`, which apm does not deploy and the replay does not compare; shared enforcement belongs in `.pre-commit-config.yaml`.
+- Keeping the install current is automatic but not free. Because the six dependencies are unpinned, deployed skills go stale whenever anyone merges. kyberforge ships a `SessionStart` hook that runs `apm outdated` at startup (~0.7s) and, when something is behind, runs `apm update --yes` and asks the host to re-scan skills (~10.4s). That rewrites `apm.lock.yaml`, so an unexplained modification to it after opening a session is expected, not a bug — commit or discard it deliberately. Note `apm install` alone will **not** pick up remote changes; it deploys from the lock. `apm update` is the command that re-resolves refs.
 - Install git hooks via `pc-run`, wiring all three stages — this repo's `.pre-commit-config.yaml` has no `default_install_hook_types`, so a plain install silently skips `commit-msg` (Conventional Commits) and `pre-push` (the 13-hook gate described below).
 - Install the `apm` CLI — four pre-push hooks shell out to it: `apm-marketplace-check`, `apm-audit-ci`, `apm-pack-check-clean`, and `check-plugin-content-sync` (via `scripts/sync-plugin-content.sh`, which wraps `apm pack`). `apm-marketplace-check` and `apm-pack-check-clean` are bare `apm …` hook entries and `apm-audit-ci` is a `bash -c` loop calling `apm` once per package, so without it the push dies with an unhelpful "command not found". Use `apm-install`, or `curl -sSL https://aka.ms/apm-unix | sh`; verify with `apm --version`.
 - Install `jq` — required by `scripts/check-manifests.sh` and `scripts/sync-plugin-content.sh`, both pre-push. These at least fail loudly (`Error: jq is required but not installed`).